Learning Forum

[epagenkopf]

I am currently working on a thermal-electric simulation for a Triply Periodic Minimal Surface (TPMS) heat exchanger designed in nTop. I am running into significant roadblocks when moving from a pure Electric simulation to a Thermal-Electric analysis in Ansys Mechanical.

What I've tried:

1. nTop to Ansys via .cbd (CDB Export):

When I export the mesh as a .cbd file from nTop, the simulation works perfectly for standard Electric runs. However, when I use the exact same setup for a Thermal-Electric analysis, the solver fails immediately. The error messages point to an incorrect element type.

1. • It seems the .cbd export is defaulting to elements that do not support the coupled thermal-electric degrees of freedom (like SOLID226/227).

   • Is there a way to force a specific element type during the import of an external mesh, or a specific nTop setting to ensure compatibility with coupled-field solvers? Or is there a way to convert a .cbd file to ensure the mesh is properly setup for a thermal-electric simulation?

2. Trying .stl

 As an alternative, I attempted to import the geometry as an .stl. While the geometry meshes successfully in Mechanical, I lose all topological intelligence.   

• The entire TPMS structure is treated as a single continuous face. Selecting any face selects every face.

• I am unable to select specific faces to apply Voltage or Heat Flux boundary conditions.

• Furthermore, using "Named Selections" based on XYZ coordinates (Location) has been unsuccessful because the software doesn't allow me to isolate a specific surface from the continuous mesh skin.

 

Questions:

• Has anyone found a reliable way to preserve Face Selections/Named Selections when moving high-complexity TPMS geometry from nTop to Ansys?

• Are there specific nTop workflows that ensure the .cbd file includes the necessary degrees of freedom for Thermal-Electric coupling? Or other methods of exporting out of nTop to a thermal-electric study?

• If I must use an .stl or a generic mesh, how can I effectively apply boundary conditions to specific "ends" of a complex lattice when coordinate-based picking fails?

Any advice on the proper way to import and mesh TPMS structures or an nTop-to-Ansys pipeline for multiphysics would be greatly appreciated.

Software Versions:

• Ansys Mechanical 2023 R2

• nTop 5.41.3

[ErKo]

 

 

 

Hello

We can no comment on this software  (ntop) .

 

As for stl, there are some ways to convert to solid bodies and so to apply the BC, loads etc in a thermal electric system.

A few videos and tutorials out there if you search.
Converting STL to 3D CAD in Ansys Discovery using SubD

 

Wait also for other forum members that might have done this to chime in (- unfortunetaly Ansys emp. can not recieve or open any files here - perhaps peteroznewman can see your file and see how it can be converted to solid geometry from stl)

All the best

 

Erko

 

 

 

[peteroznewman]

In the nTop to Ansys via .cbd mesh transfer, the order of the elements must match the desired element type. By order I mean Linear or Quadratic elements where Linear elements have no midside node while Quadratic elements have a midside node.  If the exported mesh contains linear elements, you can't assign a quadratic element type like SOLID226/227.  What is the element order in the Electric analysis?

This ChatGPT query suggests you can specify Quadratic (midside node) element during the FE Mesh creation in nTop. Specifying element order is not done at the export step, but during the mesh creation itself.

[ErKo]

 

 

 

 

Elements in thermal-electrical is 226/227 solids and 231/232 for electric

I would suggest if possible to get the stl file and convert it (as importing cdb with non solid227 elements will require non- native manipulation of cdb file whic is not supported – also we can not control the cdb file export as it comes from another tool).

In this way (stl cocnversion to solid geon.) everything is supported and native in Workbench Mech.

Kindly see if you can help with the conversion (stl).

Thank you

Erko

 

 

 

 

[ErKo]

epagenkopf - can you post how you import the cdb file and the system you use also - post also the et,1,solid187 perhaps, and eblock section (contains element info) inside the cdb file want to see what elements come out there. Thank you Erko